1. Electrical, Electronic and Computer Engineering Department, University of Pretoria, Pretoria 0002, South Africa
2. Al-Farabi Kazakh National University, 71 al-Farabi Ave., 050040 Almaty, Kazakhstan
3. Department of Chemistry, University of Agriculture, 38000 Faisalabad, Pakistan
4. Department of Theoretical and Applied Physics, African University of Science and Technology, Km. 10 Airport Road, Galadimawa, Abuja, Nigeria
5. Department of Physics, University of Pretoria, Pretoria 0002, South Africa
6. School of Chemistry, Molecular Science Institute, University of the Witwatersrand, Private Bag 3, P O Wits, Johannesburg 2050, South Africa
7. Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria